Vulcanized tire size allocating method,tire manufacturing method, and vulcanizing process setting method.

ABSTRACT

A family of tire sizes are classified into plural groups every tact time and only sizes belonging to the same group are selected from the family of tire sizes and allocated in a plurality of vulcanization stations vulcanizing tires, whereby tires of plural sizes can be vulcanized at a mixed state for a given tact time without requiring middle stock for green tires.

TECHNICAL FIELD

This invention relates to a size allocating method in the vulcanizationof tires, a method of producing a tire and a setting method ofvulcanization process, and more particularly to a method capable ofefficiently vulcanizing tires of plural sizes.

BACKGROUND ART

In a vulcanization system for vulcanizing plural tire sizes in order toachieve a high productivity, there has hitherto been conducted a methodwherein tires are vulcanized in a plurality of vulcanization machinesfor a shortest vulcanizing time every the size. According to thismethod, however, if the size of the tire to be vulcanized in thevulcanization machine differs, the vulcanizing time differs, so that atact time differs every the vulcanization machine. This comes intoproblem because even if green tires are shaped at a constant tact time,a vast middle storage space for the green tires should be disposedbetween the tire shaping system and the tire vulcanizing system forpreventing the lack of stock of the green tires.

The invention has been made considering the above problem and is toprovide a size allocating method of tire vulcanization capable ofefficiently vulcanizing at a constant tact time without requiring themiddle storage for the green tires even if tires of plural sizes aremixed, and a method of producing tires as well as a setting method ofvulcanization process.

DISCLOSURE OF THE INVENTION

The invention is made for achieving the above object and the summary andconstruction thereof are as follows.

<1> A method of allocating tire size in tire vulcanization in which atire size to be vulcanized is allocated in each vulcanization station ofa vulcanization system having a plurality of vulcanization stations andvulcanizing tires of a previously given family of tire sizes, whereinwhen a plurality of tact times are previously set on the vulcanizationsystem and only tire sizes having a vulcanizing time capable ofrealizing each tact time are collected to form plural groups specifiedby the tact time and tire sizes belonging to the same group among theabove given family are selected to allocate in each vulcanizationstation, tire sizes are made different in at least two vulcanizationstations at any size allocation among a series of size allocationsrenewed every changeover of size.

According to the invention, the size allocation is carried out byselecting only the tire sizes belonging to the group corresponding toone tact time, so that the tires can be vulcanized in synchronizationwith the tire shaping step while making the tact time constant and themiddle storage for the green tires can be controlled. Also, the tiresizes are made different in at least two vulcanization stations at anysize allocation, so that tires having plural sizes can be vulcanized ata mixed state.

<2> The invention according to the item <1> is a size allocating methodin tire vulcanization, wherein a unity vulcanizing time is set as astandard vulcanizing time capable of realizing a tact time every thetact time and a tire size capable of vulcanizing at the unityvulcanizing time is included in the group in correspondence to the tacttime and also a tire size capable of vulcanizing at a vulcanizing timeof not more than Tp represented by the following equation (A) even intire sizes not vulcanizing at the unity vulcanizing time is included inthe group in correspondence to the tact time:Tp=TT×N−t  (A)wherein TT, N and t are mentioned as follows.

-   TT: tact time in correspondence with each of the groups-   N: number of vulcanization stations in the vulcanization system-   t: total of a time required for charging a tire of a target size    into the vulcanization station and a time required for discharging    the tire from the vulcanization station

According to this invention, even in tire sizes not vulcanizing for theunity vulcanizing time, if tires have a size capable of vulcanizing at avulcanizing time of not more than Tp represented by the equation (A),they are included in the same group, so that a greater number of tirescan be produced in a short cycle time.

<3> The invention according to the item <1> or <2> is a size allocatingmethod in tire vulcanization, wherein the group includes at least twotire sizes having different vulcanization temperatures.

According to this invention, the sizes having different vulcanizingtemperatures are included in one group, so that a greater number ofsizes can be packed in one group and the production of multi-size mixedtires can be carried out efficiently.

<4> The invention according to any one of the items <1)-<3> is a sizeallocating method in tire vulcanization, wherein the family of tiresizes is classified into 2-6 groups.

According to this invention, the number of the groups is 2-6, so thatthe vulcanization can be conducted efficiently. When the number ofgroups is 1, the range of sizes targeted in the vulcanization systemshould be made small and hence the ability of the system correspondingto the sizes is narrowed, while when the number of groups exceeds 6, thechangeover between the groups becomes large and the loss due to the stopof the system between the changeovers can not be ignored.

<5> The invention is a method of producing a tire by vulcanizing a tirebased on the size allocating method according to any one of the items<1>-<4> in which the tire is vulcanized at a tact time corresponding tothe respective size allocation.

According to this invention, the tire is vulcanized at a constant tacttime based on the aforementioned size allocating method, so that even ifplural tire sizes are produced at a mixed state, the tires can bevulcanized in synchronization with the tire shaping step to control themiddle storage for the green tires.

<6> The invention according to the item <5> is a method of producing atire, wherein the tire is shaped at the same tact time as the given tacttime of the vulcanization system vulcanizing the tire.

According to this invention, the tact time is made same between thevulcanization system and the shaping system, so that the middle storagefor the green tires can be controlled.

<7> The invention is a method of setting vulcanization process, in whichin case of setting the vulcanization process for tires produced by theproduction method described in the item <5> or <6>, a vulcanizing timeis first set and then a vulcanizing temperature is set based on thevulcanizing time.

According to this invention, the vulcanizing time is first set, so thatthe vulcanizing time can be set so as to correspond to the same tacttime on various sizes to conduct the size allocation comprising manydifferent sizes and the multi-size mixed production can be carried outefficiently.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an embodiment of size allocation.

FIG. 2 is a time chart of a vulcanization system corresponding to acertain allocation.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the invention will be described with reference to FIGS. 1and 2. Moreover, the “size allocation” used herein means the arrangementof tire sizes to be vulcanized in each of the vulcanization stations inthe planning of the production. Also, the “vulcanizing time” means atime from the closing of a vulcanization mold receiving an uncured tireto opening the vulcanization mold. Furthermore, the vulcanizationprocess is vulcanization conditions defined in the production of a tirehaving a certain size such as vulcanizing time, vulcanizing temperature,pressure inside bladder, a mold applied and the like. The “vulcanizingtemperature” used herein means a highest temperature defined in thevulcanization process among temperatures set in a heating apparatus forvulcanizing the tire, and the temperature set in the heating apparatusmeans a set temperature of an electric heater or the like as the heatingapparatus or a set temperature of a heating fluid when the heating ofthe heating apparatus is conducted by passing the heating fluid througha platen or the like.

The vulcanization system illustrated in this explanation comprises fourvulcanization stations and one mold opening-closing station. The moldopening-closing station repeats an operation on the respectivevulcanization station that the mold taken out from the vulcanizationstation is opened to take out a vulcanized tire from the mold and anuncured tire is placed in the mold to close the mold and then the moldis returned to the vulcanization station.

Table 1 shows a family of tire sizes targeted in the vulcanizationsystem every group. The family of tire sizes to be vulcanized in thissystem is classified into three groups FA, FB and FC, each of whichgroups is constituted with plural different sizes. For example, thegroup FA comprises (n1+m1) sizes of size FA₁-FA₂, . . . , FA_(n1) andFAX₁, FAX₂, . . . , FAX_(m1). In the sizes of FA₁-FA_(n1), thevulcanizing time is a-minutes, while the vulcanizing time in the sizesof FAX₁-FAX_(m1) exceeds a-minutes. Among these sizes, the vulcanizingtemperature differs between at least the sizes FA₁ and FA_(n1). Thesizes FA₁-FAX_(m1) are lines up in an order that the vulcanizingtemperature is low. TABLE 1 Group Size FA FA₁, FA₂, . . . , FA_(n1),FAX₁, . . . , FAX_(m1) FB FB₁, FB₂, . . . , FB_(n1), FBX₁, . . . ,FBX_(m1) FC FC₁, FC₂, . . . , FC_(n1), FCX₁, . . . , FCX_(m1)

Similarly, the vulcanizing time corresponding to FB₁-FB_(n2) isb-minutes and the vulcanizing time corresponding to FC₁-FC_(n3) isc-minutes, while the vulcanizing time in the sizes FBX₁-FBX_(m2) exceedsb-minutes and the vulcanizing time in the sizes FCX₁-FCX_(m3) exceedsc-minutes. Also, these sizes are lined up in an order that thevulcanizing temperature is low. For the sake of convenience in thefollowing explanation, a shortest vulcanizing time in the group iscalled as a unity vulcanizing time of the respective group. That is, theunity vulcanizing times of the groups FA, FB, FC are a-minutes,b-minutes and c-minutes, respectively, in this order.

When the feature of the grouping is explained in the above embodiment,each of the groups is classified so as to include at least two sizesbeing the same in the vulcanizing time and different in the vulcanizingtemperature. For example, in the sizes FA₁ and FA_(n1) of the group FA,the vulcanizing time is the same as a-minutes, but the vulcanizingtemperature of FA₁ is lower than the vulcanizing temperature of FA_(n1).The tires of size FA1 were vulcanized in the conventional productionmethod, in which the vulcanizing time is set to a shortest one every thesize, based on such a vulcanization process that the vulcanizingtemperature is as high as that of FA_(n1) and the vulcanizing time isshorter than a-minutes.

The degree of vulcanization determining the quality of the tire isdependent upon both of the vulcanizing time and the vulcanizingtemperature. In a given temperature range are existent many combinationsof both giving the same vulcanization degree. In the invention differentfrom the conventional determining method of vulcanization process, thereis an essential feature that a vulcanizing time on a given size is firstdetermined and then a vulcanizing temperature is determined from avulcanization degree most suitable for tires of this size to setvulcanization process for such a size. In this way, the vulcanizationprocess is determined, whereby the vulcanizing time can be classifiedinto three groups having the respective unity vulcanizing times as inthe above embodiment though the vulcanizing time is all different everythe size in the conventional technique. Thus, the sizes in the samegroup are allocated in each of the vulcanization stations to make thetact time constant, whereby the middle storage can be downsized.

The procedure of grouping the family of tire sizes into plural groups asmentioned above is as follows. At first, plural possible tact times inthe vulcanization system capable of vulcanizing tires in synchronizationwith the tire shaping step are set considering the production capabilityof the tire shaping step. Then, tire sizes of vulcanizing time capableof realizing the tact time are collected and grouped in a family of tiresizes as the feature of grouping according to the invention. Even in thesame size, if the vulcanizing time is short, some of these tact timescan be realized, and hence there can be taken some grouping methods, butthe following grouping is preferable.

That is, the unity vulcanizing time as previously mentioned is set everythe tact time as a standard vulcanizing time capable of realizing such atact time. Then, the grouping is made from a group corresponding to ashort tact time in turn and tire sizes capable of setting thevulcanizing time to the unity vulcanizing time corresponding to the tacttime are made belonging to the group. In this case, even if tire size isset to only a vulcanizing time longer than the unity vulcanizing timecorresponding to a certain tact time, a size having a vulcanizing timecapable of realizing the tact time, i.e. a size having a vulcanizingtime of not more than Tp in the aforementioned equation (A) is madebelonging to a group corresponding to such a tact time.

Thus, a greater number of tire sizes can be made belonging to a groupcorresponding to a short tact time to enhance the productivity of thevulcanization.

FIG. 1 is a diagram illustrating size allocations on the fourvulcanization stations in the above vulcanization system. Allocation1-Allocation 150 allocate sizes of group FA to each vulcanizationstation, and Allocation 151 or later allocate sizes of group FB to eachvulcanization station. In Allocation 1, FA₁, FA₂, FA₃ and FAX_(m1) areallocated to vulcanization stations 1, 2, 3, 4, respectively. InAllocation 2, the size in the vulcanization station 2 is changed over toFA₆, and then the size of the vulcanization station 3 is changed over toFA₄ in Allocation 3. In this way, the allocation is transited to a newone every the changeover of the size at any vulcanization station. Also,the sizes selected from the same group FA are changed over up toAllocation 150. At Allocation 151, sizes of group FB are allocated toall of the vulcanization stations, and thereafter sizes selected fromthe same group FB are changed over.

FIG. 2 is a time chart showing a timing of an operation made in each ofthe vulcanization stations at the vulcanization system conducted by acertain size allocation. Operation A1 represents the vulcanization of atire, A2 represents the charging of the tire including the placing of anuncured tire in a vulcanization mold and the closing of the mold, A3represents the discharge of the tire including the opening of the moldand take-out of a vulcanized tire from the mold, and A4 representsnon-operation of a state conducting no operation in the vulcanizationstation. In the vulcanization system, in order to downsize the middlestorage, this vulcanization system operated in synchronization with theshaping system at a constant tact time TT determined from a tact time ofthe shaping. That is, it is required to discharge one vulcanized tireevery the tact time TT. When the number of the vulcanization stations isN, a time of one cycle at a series of operation at the respectivevulcanization station, i.e. a cycle time CT should be a constant timeobtained by multiplying tact time TT and N.

In the conventional production method, the cycle time CT in each of thevulcanization stations can not be made constant because the vulcanizingtimes are all different every sizes. In the invention, however, thecycle time CT can be made constant by allocating tire sizes belonging tothe same group to the respective vulcanization station. This isdescribed below. When the time chart of FIG. 2 is corresponded toAllocation 1, the vulcanization station 1 vulcanizes a tire of size FA₁in which the vulcanizing time T is a unity vulcanizing time of a-minutesand leaves a time t_(α) of non-operation A4 as shown in the figure, sothat the operation of one cycle can be completed at a cycle time CT ingood time. That is, when the unity vulcanizing time of the allocatedgroup FA is shorter than a time obtained by subtracting a total time(t₁+t₂) required for the charge of tire A2 and discharge of tire A3 fromthe cycle time CT, the operation can be continued at a constant cycletime CT.

On the other hand, the vulcanization station 4 vulcanize a tire of sizeFAX_(m1) belonging to the group FA but having a vulcanizing time Tαlonger than the unity vulcanizing time of a-minutes. Even in this case,since a time obtained by adding (t₁+t₂) to T_(α) is shorter than thecycle time CT, the vulcanization system can be operated withoutdestroying the constant cycle time CT even when the size FAX_(m1) isallocated together with the size such as FA₁ or the like having aprocess of the unity vulcanizing time in the group FA. That is, evenwhen the vulcanizing time is longer than the unity vulcanizing time,tires having a vulcanizing time shorter than a time obtained bysubtracting the total time required for the charge and discharge of thetire (t₁+t₂) from a multiplied value of the tact time TT of thevulcanization system and the number of vulcanization stations N can beincluded in the same group, and hence sizes of a wider range can begrouped in one group to cover the given size range with a limited group.

Although the number of vulcanization stations is 4 and the number oftact times or groups is 3 in the above explanation, similar sizeallocations can be conducted even in the numbers other than the aboveand the similar effects can be obtained.

INDUSTRIAL APPLICABILITY

As seen from the above, since the vulcanizing times are all differentevery the sizes in the conventional production method, when the pluraltire sizes are allocated, the vulcanization can not be carried out at aconstant cycle time and hence a vast middle storage for green tires isrequired. In the invention, sizes capable of completing the operation ofone cycle in the same cycle time are summed up in one group and the sizeallocation is carried out so as to make sizes in each of thevulcanization stations belonging to the same group, so that thevulcanization can be conducted at a constant cycle time and the middlestorage can be made approximately zero by synchronizing with the tireshaping system.

1. A method of allocating tire size in tire vulcanization in which atire size to be vulcanized is allocated in each vulcanization station ofa vulcanization system having a plurality of vulcanization stations andvulcanizing tires of a previously given family of tire sizes, whereinwhen a plurality of tact times are previously set on the vulcanizationsystem and only tire sizes having a vulcanizing time capable ofrealizing each tact time are collected to form plural groups specifiedby the tact time and tire sizes belonging to the same group among theabove given family are selected to allocate in each vulcanizationstation, tire sizes are made different in at least two vulcanizationstations at any size allocation among a series of size allocationsrenewed every changeover of size.
 2. A method of allocating tire size intire vulcanization according to claim 1, wherein a unity vulcanizingtime is set as a standard vulcanizing time capable of realizing a tacttime every the tact time and a tire size capable of vulcanizing at theunity vulcanizing time is included in the group in correspondence to thetact time and also a tire size capable of vulcanizing at a vulcanizingtime of not more than Tp represented by the following equation (A) evenin tire sizes not vulcanizing at the unity vulcanizing time is includedin the group in correspondence to the tact time:Tp=TT×N−t  (A) wherein TT, N and t are mentioned as follows. TT: tacttime in correspondence with each of the groups N: number ofvulcanization stations in the vulcanization system t: total of a timerequired for charging a tire of a target size into the vulcanizationstation and a time required for discharging the tire from thevulcanization station.
 3. A method of allocating tire size in tirevulcanization according to claim 1, wherein the group includes at leasttwo tire sizes having different vulcanization temperatures.
 4. A methodof allocating tire size in tire vulcanization according to claim 1,wherein the family of tire sizes is classified into 2-6 groups.
 5. Amethod of producing a tire by vulcanizing a tire based on the sizeallocating method according to claim 1, in which the tire is vulcanizedat a tact time corresponding to the respective size allocation.
 6. Amethod of producing a tire according to claim 5, wherein the tire isshaped at the same tact time as the given tact time of the vulcanizationsystem vulcanizing the tire.
 7. A method of setting vulcanizationprocess, in which in case of setting the vulcanization process for tiresproduced by the production method as claimed in claim 5, a vulcanizingtime is first set and then a vulcanizing temperature is set based on thevulcanizing time.